What did the membership in the Suicide Society of the Summer Session involve in A Separate Peace?

Membership in the Super Suicide Society of the Summer Session involves jumping out of a specific tree strategically situated with a branch hanging out over the Devon River. The Society, spontaneously formed by Finny and loosely modeled on the myriad clubs that are a part of boarding school tradition, meets every night. There are two Charter Members of the Society, Finny and Gene, and the other attendees are trainees. Finny and Gene are the only two who...

Membership in the Super Suicide Society of the Summer Session involves jumping out of a specific tree strategically situated with a branch hanging out over the Devon River. The Society, spontaneously formed by Finny and loosely modeled on the myriad clubs that are a part of boarding school tradition, meets every night. There are two Charter Members of the Society, Finny and Gene, and the other attendees are trainees. Finny and Gene are the only two who have jumped out of the tree; the others have not yet worked up the nerve to accomplish the dangerous stunt, which will allow them to become full-fledged members themselves.

Gene, who has been goaded by Finny into jumping from the tree into the river, is fearful of the feat he is required to perform with Finny at the opening of every meeting. He sees the tree as

"an irate, steely black steeple beside the river,"

and feels that jumping from such a dangerous and precarious perch is "a crazy idea." Still, for reasons he does not fully understand, Gene allows himself to be swayed and jumps with Finny time after time. The other boys are mesmerized by Finny's glib but well-meaning charisma as well, and persist in attending the meetings of the Super Suicide Society of the Summer Session night after night, trying to convince themselves to "save face" and jump from the tree like Gene and Finny, thus joining the ranks of the Charter Members of the club.